The first thing we need to do is create a user to run your DC++ client under. We do this because ipfw doesn't currently support filtering by program, but it does support filtering by user, so we can create ipfw rules that apply only to a specific user and run your DC++ client as that user I'm using "dc" as my user, you can use whatever you want.

You can create a new user by doing the following

Next we need to create the ipfw rules.

Open a Terminal to run the following commands. This can be done from "Applications -> Utilities". Remembering to use the right User.

For these filters to work you have to run your client as the dc user

You should now your client running as user dc and with external connections blocked. You will need the following line to enable access control for the user 'dc'

To run an application as another user enter the following lines in terminal

Enter the password that you gave the user dc when you created the user

NB. The rules should reset when you reboot, so you might have to reconfigure them after every reboot or script them to run at startup. Please confirm with somebody on the hub if the rules are persistent or reset at every reboot.